Standard frequency system



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u N uw; gf j N 0, o? Eg v E KQ o l o: "5, l l l a a N Y l l /NVENTORWAMARR/SON A TTOR/VE V Patented July 20, 1937 UNITED STATES PATENTOFFICE STANDARD FREQUENCY SYSTEM Application September 22, 1934, SerialNo. 745,098

Z4 Claims. l (Cl. ,T90- 4) This invention relates to standard orconstant frequency systems and more particularly to regulating the phaseof the standard frequency current.

The invention also relates to the application of this phase regulatedstandard frequency current to indicate the correct time and to controlthe frequency and regulate the integrated phase of an alternatingcurrent power supply network so that the frequency of this power supplysystem .may be utilized in devices to indicate the correct time.

In standard or constant frequency systems, various means and devices areemployed to prevent any change in the frequency thereof. It is thereforevery difficult, undesirable and, in some cases, impracticable, toreadily adjust the phase of the output current of such a system in anydesired manner to conform to different sets of conditions.

It is the object of this invention to provide a phase adjusting orregulating device which will adjust the phase of an alternating currenteither continuously and uniformly or intermittently at any uniform andspecified rate through any phase angle however large so that the phaseof the standard frequency current may be regulated in any desired mannerto conform to any set of specified conditions as, for example, timesignals.

A feature of the invention is that means are provided to substantiallyeliminate the effect of stray fields and couplings upon the phaseregulating device.

Still another feature of the invention is that changes in the output ofthe phase regulating or adjusting device or changes in its loadimpedance are prevented from affecting the phase or frequency of itsoutput current.

Furthermore, the frequency of an alternating current power supply systemwhen used to furnish time service is usually compared with a masterclock and is adjusted either automatically or manually in accordancewith this clocku so that clocks run from the power system will indicatethe same time as the master clock. This master clock will vary some fromthe correct time so that it will be necessary to set it from time totime. When the phase and frequency of the power system is manuallyadjusted in accordance with a master clock, this clock may be set bytime signals or in accordance with any other observations and thefrequency and phase of the power system manually regulated in accordancewith the clock. However, when it is desired to automatically control thefrequency and phase of the power supply system in accordance with amaster clock, it is very difficult tovcorrect or set the master clock inaccordance with time signals and, at the same time, have the clocksconnected to the power system also automatically set to indicate thecorrect time in accordance with the master clock. This is particularlytrue when the power system is large and has many motors and generatorsconnected to it since it is impossible to change in a rapid or abruptmanner 10 either the angular velocity or relative angular position ofthe large rotating masses of thegenerators and motors connected to thepower system.

A further object of this invention, therefore, 15 is to provide a systemfor controlling the frequency and regulating the phase of a power systemby varying or regulating the phase of a standard or control frequency inaccordance with time signals and then controlling the frequency andregulating the integrated phase of a power supply system in accordancewith the phase and frequency of this phase regulated standard or controlfrequency. In this manner, it is possible to automatically set andregulate the power sup- 25 ply frequency so that all the electric clocksdriven by synchronous motors which are connected to it will beautomatically adjusted and set in accordance with time signals so thatthey will indicate the correct time. 30

A feature of the invention is that means are provided to regulate thefrequency and relative phase of any and all of the generators connectedto the power supply system in any desired manner from the centralstation. 0

A further feature of the invention is that the distribution or divisionof load between the' various power houses, power generators and powergenerators ofthe power system may be controlled from a central switchingpoint to reduce the circulating current and power in the connecting tielines between the various generating stations.

Another object of this invention is to provide an improved andsimplified modulating arrangement for comparing the frequency and phaseof a standard frequency current and the frequency and phase of apolyphase alternating current power system.

A feature of this modulating arrangement is 50 that it may employgas-filled glow discharge or thyratron type tubes.

A further object of this invention is to provide a flexible and reliablestandard frequency distribution system for distributing standard fre- 55quency current to a large number of clocks and power systems.

rent.

A feature of this invention is that means are provided to automaticallycompensate for variations in the distribution system due to weatherchanges.

In brief, the invention provides a source of constant frequency currentsuch as disclosed by W. A. Marrison in U. S. Patent 1,784,844, December16, 1930 and W. A. Marrison Patent 1,935,325, November 14, 1933, both ofwhich are hereby made partI of this description as if fully includedherein.

The standard frequency current then passes through a phase regulatingdevice. This device comprises a phase splitter for securing currents oftwo phases, each phase of which is supplied to the input circuit of avacuum tube. Outputs from these two tubes are then used to secure arotating magnetic field in which a pickup coil may be rotated in anydesired manner at a designated speed so that the currents of the desiredfrequency and phase are induced in it. This coil is then connected tothe output of the phase regulating and adjusting device through a thirdvacuum tube amplifier which eliminates the effect of variations of theload impedance on the frequency and phase of the output current.

This phase regulated standard frequency current may then be employed torun a. large number of electric clocks which are driven by synchronousmotors. Time indicated by these synchronous clocks may then beautomatically and simultaneously adjusted in accordance with timesignals by the operation of the phase adjusting or regulating device.

This phase regulated standard frequency current may also be used tocontrol the frequency and regulate the phase of a power supply system.To accomplish this, the phase regulated constant frequency current istransmitted to the various' power houses either over a power linecarrier system or by a special line. At these power houses, the standardfrequency current is compared by means of a modulating device with thephase and frequency of the power current generated at the respectivepower houses. lf desired, the comparing or modulating device may becoupled so as to control either the throttle or the governor of theprime movers driving the generators located at the power house so thatthe frequency and phase of the power supply system is controlled inaccordance with the phase and frequency of the regulated standardfrequency cur- In order to insure continuity of service it may bedesirable to provide a secondary standard of constant frequency currentat each of the power houses which are also controlled by the standardfrequency current received over the line. This secondary standard willsupply the control frequency for the power system in case the supply ofthe standard frequency current transmitted to the power house, for anyreason, is interrupted.

It is to be understood that a similar secondary frequency standardsource may be provided at any of the clock or frequency systemsconnected to or controlled by the standard frequency. It may also bedesirable to provide these secondary standard systems at various pointsin the standard. frequency distribution network.

By transmitting this phase regulated constant frequency current to thevarious generating stations or generators'of a system at relativelydifferent phase angles, the division of load between the variousgenerators and power houses may be readily controlled so that anydesired load distribution may be secured and maintained. Il' it isdesired, this control may be secured from any centralized control pointby providing phase regulating devices at this control point whichregulate the phase of the standard frequency current transmitted to eachof the power houses of the system.

These and other features of the invention may be more readily understoodfrom the following description of several embodiments of the 1nventionwhen read with reference to the drawings, in which:

Fig. 1 shows the arrangements of Figs. 2 to 6;

Figs. 2 to 6 illustrate detailsl of a standard frequency system, thephase and frequency of which is adjusted in accordance with time signalsand employed to operate a number of clock systems as well as to regulatethe phase and frequency of alternating current power supply systems;

Figs. 2-A, 7 and 8 show an alternative phase adjusting and regulatingmeans to that shown in Fig. 2. The arrangement shown in Fig. 8 issimilar to the arrangement shown in a patent application of L. A.Meacham, Serial No. 686,352, filed August 23, 1933, which issued asPatent 2,004,613 on June 11, 1935;

Figs. 9 and 10 show alternative modulating circuits for regulating thefrequency of a power system in accordance with the standard frequency;and

Fig. 11 shows one method of increasing the torque of the control motorin case considerable torque is required to operate the throttle orgovernor of a prime mover in the power system.

A general description of a typical standard frequency system, inaccordance with this invention, will now be given with reference toFigs. 2 to 6 of the drawings when arranged in accordance with Fig. 1.Starting with Fig. 2, 2| represents a source of standard or constantfrequency alternating current. This source may be of any convenient orsuitable form as, for example, those illustrated by W. A. Marrison in U.S. Patents 1,784,844, December 16, 1930 and 1,935,325, November 14,1933. This source may contain one or more alternating current generatorsand means for comparing the relative frequencies of the variousgenerators as disclosed in the patents above referred to. The frequencyof the output of source 2| may be changed by multi-vibrator circuit 22which may be of any suitable form well known in the art, such asdisclosed in a patent application of L. A. Meacham, Serial No. 734,085filed July 7, 1934 which issued as Patent 2,022,969 on December 3, 1935,in U. S. patent to- B. Van der Pol 1,744,935, January 28, 1930, or by L.M. Hull and J. K. Clapp in the Proceedings of the Radio Engineers onpages 252 to 271 of vol. 17, No. 2 for February, 1929. A` standardfrequency or time system 26 is shown connected to the output ofmulti-vibrator circuit 22. This system may be any standard frequencysystem, such as one similar to the one about to be described or it maybe one used to control the frequency of radio stations as described inU. S. patents to R. Bown 1,490,958, April 22, 1924 or L. Espenschied etal. 1,711,560, May 7, 1929 which are made part of this description. Theoutput from multi-vibrator circuit 22 is also connected tomulti-vibrator circuit 23 where the frequency of the current is furtherchanged. A portion of the current then passes through stili anothervibrator circuit 24 which changes the frequency so that it is suitablefor operating a. frequency integrating and recording device, such asclock 25. This clock 25 may be used to check the accuracy of thestandard frequency obtained from the alternating current generator 2|. Afurther portion of the current from multi-vibrator circuit 23 passesthough transformer 21 over line |62. This line |62 may extend somedistance from the constant frequency source or multi-vibrator 23 toterminals 5| of transformer 21. Condenser 28 and resistance 29 areconnected in series with each other and to the output of the transformer21. Since the same current must flow through -both condenser 28 andresistance 29, the voltage drop across the condenser 28 will be ninetydegrees out of phase with the voltage drop across resistance 29. Thesetwo voltage drops may be made equal by4 appropriate choice of the valueof the capacity of condenser 28 and of the resistance 29. These twovoltage drops are applied to the grids or input circuits of vacuum tubes39 and 3|, respectively. The outputs of these tubes are connected tocoils 38 and 49, and 39 and 4| which are Wound on ring 42. Ring 42 ispreferably made of compressed dust of magnetic materials such asnickel-iron alloys but may be of any suitable magnetic material such aslaminated iron, silicon steel, or hydrogenized iron. The two coils 38and 49, as well as 39 and 4|, are Wound in opposite directions so as toproduce a magnetic field diametrically across the ring. It should benoted that coils 39 and 4| are spaced ninety degrees around the ringfrom coils 38 and 49 so that when these coils are energized by theoutput currents from tubes 39 and 3| which are in phase quadrature, arotating eld is produced which rotates at a speed proportional to theinput frequency from the standard frequency source 2| as changed bymulti-vibrator circuits 22 and 23. Condensers 32 and 33 are connected inparallel with coils 38 and 49 and 39 and 4|, to tune them to resonate atthe impressed frequency and also to make minor adjustments in therelative phase between the two currents from tubes 39 and 3|.

An armature 43 is mounted on shaft 16 and is located in the rotatingmagnetic field across the ring 42. Armature 43 is usually made of thesame magnetic material as ring 42 but may be of any other suitablemagnetic material. Armature 43 is rotated by motor 19 through gears 68and 61 at any desired or specified speed of say AF revolutions persecond. The pick-up coil or winding 44 on armature 43 Will then haveinduced in it a current of a frequency equal to FiAF, where F is thestandard frequency and the sign depends upon the relative directions ofrotation of armature 43 and the rotating magnetic field across the ring42. The winding 44 on armature 43 is connected through slip rings 45 and46 to the input circuit of tube 41 through terminals 59 where thecurrent induced in winding 43 is amplified by tube 41 and is transmittedthrough the output transformer 48 to terminals 49. A portion of thecurrent from terminal 49 then passes through another multi-vibratorcircuit 52 which again changes its frequency so that it is suitable forop-erating small synchronous motors which in turn drive clockmechanisms. The clock 55 connected to bus 56 is supplied by the outputcurrent from multi-vibrator circuit 52. The time indicated by clock 55may be periodically checked by time signals received by radio receiver58 from antenna 51. It is to be understood, however, that this clock maybe checked in any other convenient manner, such as observations fromstars or by telegraph or telephone signals from the average time asindicated by a group of Observatories, such as furnished by the UnitedStates Government. In addition, a suitable recording and comparingdevice 59 such as described in U. S. patent to F. D. Urie 1,202,925,October 31, 1916 may be connected between buses 56 and radio receiver 58to automatically compare and record the time signals as received withthe frequency of the alternating current flowing in buses 56. Radioreceiver 58 may also be used to compare the frequency of source 2| withtime signals by means of clock 25 either visually or by any suitableautomatic means provided clock 25 and receiver 58 are sufficiently closetogether. If this is not the case, a separate radio receiver 399 may beprovided so that the time indicated by clock 25 may be compared withtime signals.

Also connected to terminal 49 is an amplifier 53 which will amplifystandard frequency current so that it may be transmitted to a distantmultivibrator circuit 54 where its frequency will be altered suitablyfor operating a similar standard frequency or time system. It is to beunderstood that any of the multi-vibrators 22, 23, 24, 52, or 54 may beomitted in case it is not necessary to alter the frequency of thestandard frequency source. In addition, amplifier 53 may be omitted oradditional amplifiers connected in the line to multi-vibrator 54depending upon the attenuation of this line.

Fig. Z-A shows an alternative arrangement for armature 43. Here windings15 and 16 are wound upon a ring 14 which is mounted upon shaft 16 sothat it may be rotated in a manner similar to that described forarmature 43. Both this ring armature and the drum armature have beenfound to be suitable for obtaining a very uniform and regular phasechange with the rotation of the armature. It has yalso been found thatthe frequency and phase change of the current in the pick-up coil ismore uniform and regular when the airgap between the armature and thering is as short as possible.

It should also be noted that the quadrature voltage drops acrosscondenser 28 and resistance 29 (see Fig. 2) are applied directly to theinput circuits of tubes 30 and 3|. This substantially eliminates theeiects of stray capacities or couplings upon the phase relationship ofthese two quadrature voltages which tend to change the magnitude andalso the relative phases of these two voltages. In addition, the vacuumtube 41 prevents changes in the load impedance or output current frommaterially affecting the phase and frequency of the voltage induced inthe pick-up l coil and thus the phase and frequency of the outputvoltage.

Referring again to Fig. 2, motor armature 19 and field 1| are connectedthrough key 12 and contacts 64 to a source of power 13. A revolutioncounter 69 is also connected to shaft 16 and is employed to record thetotal number of revolutions made by shaft 16 and armature 43. Dial 69 isalso connected to shaft 16 through suitable gears such vas 61 and 66 andfriction clutch 65. Dial 69 is provided With an indicator 6| and knob62. Cam 63 rotates with dial 69 and controls contacts 64.

Dial 69 may be calibrated in any suitable unit, such as seconds,thousandths of a second, or cycles. Assume, for purposes ofillustration, that dial 69 is calibrated in hundredths of a second.Assume further that when time signals are received from antenna 51 byradio receiver 58, clock 55 is 0.05 second fast. Then, some time beforethe next set of time signals or during the following day or wheneverdesirable, dial 60 will be rotated in the direction of the arrow F sothat indicator 6| will indicate 0.05 second. This will also rotate cam63 which will cause it to close contacts 64. It should be noted that therotation of disc 60 does not rotate armature 43 since it is connected toshaft 16 upon which armature 43 is mounted through friction clutch 65which allows cam 63 and dial 60 to be rotated without rotating gears 66and 61 and armature 43. Contacts 64, in closing, connect power fromsource 13 to key 12. Then, when it is desired to correct clock 55, aswell as all the other electric clocks which are run by synchronousmotors and areconnected to the standard frequency system, key 12 isoperated so as to close the F contacts. This completes the circuit tomotor armature 10 and field 1| so that armature 43 will be rotated in adirection to cause a correction to the reading of clock 55 as well asthe other electric clocks connected to the system. The speed of motor10, as well as the gear ratio between motor 10 and shaft 16, is adjustedso that the adjustment in the frequency and phase of the current andthus the time indicated by clock 55 is made at any desired or specifiedrate.

The term time signals as used in the above example and 'this specicationincludes both single and the average or mean of a plurality ofobservations of suitable signals. In some cases it v may be desirable toattempt to correct for slight random errors in -the observations or timesignals. This may be done by making the best possible estimate of theprobable error of the observation or time signal based upon all previoustime signals and other data. The observation or time signal may then becorrected and the frequency or clocks of the system adjusted inaccordance with this corrected observation or time signal.

Bus-bar 56 extends from Fig. 2 to Fig. 3 where numerous forms ofdistribution systems are shown. For example, carrier equipment 82 isconnected to bus-bar 56 and, in turn, to line 83 which may extend aconsiderable distance and include suitable amplifiers and otherapparatus (not shown) to the carrier apparatus 84 located near clocksystem 85. In case of an unusually long line, as line 88, it may bedesirable to provide phase adjusting apparatus such as disclosed in U.S. patents to H. A. Affe] 1,450,966, April 10, 1923; H. Nyquist1,615,911, February 1, 1927; and H. Nyquist 1,688,725 September 11, 1928which are hereby made part of this description, and illustrated at 86either before or after a. carrier apparatus, such as 81, in order tocompensate for phase changes occurring in line 88 due to temperature andgeneral Weather conditions. In this case, the standard frequency currentis applied to numerous channels of a multi-channel carrier system inwhich one channel is terminated in carrier equipment illustrated at 89and supplies clock system 90. Another channel terminates in carrierequipment 9| and supplies standard frequency to clock system 92, While athird channel is shown terminating in carrier equipment 93 and supplyingclock system 94. In other cases it may be desirable to connect clocksystems directly to bus-bar 58 over suitable lines, such as 91. Clocksystem 95 illustrates such a system connected to bus-bar 56 by line 91.In case the line becomes unusually long, it may be necessary to providereceiving amplifiers, as illustrated at 96 and 99, for clock systems 98and |00. In case of extremely long lines, it may be desirable to providea. transmitting amplifier 18 connected to-line 19 in addition to areceiving amplifier 80, for supplying a clock system 8|. In addition,line 19 may pass through other suitable amplifiers and phase adjustingapparatus. It should be noted that transmitting amplifier 18 provides anadditional safeguard in that it prevents any troubles occurring on line19 from affecting the current supplied to any of the other linesconnected to bus-bars 56. For this reason, it may be desirable toprovide a transmitting amplifier for each of the lines and systemsconnected to bus-bars 56 so that any trouble or abnormal conditionsarising on any of the lines will affect only the lines in trouble butwill not affect the entire system. These amplifiers may be of anysuitable type including both constant gain and constant output types ofamplifiers and also feedback amplifiers such as described in a patentapplication of H. S. Black Serial No. 411,224, filed December 3, 1929which issued as Patent 2,003,282 on June 4, 1935.

These clock systems 8|, 85, 90, 92, 94, 98 and may be of any type suchas employed in schools, hotels, hospitals, public buildings, railroads,train dispatching, industrial organizations, telephone systems asdescribed in U. S. patent to W. B. Prince 1,863,141, June 14, 1932,telegraph systems such as described in U. S. patent to T. A. McCann1,940,764, December 26, 1933, or in clock and watch adjusting apparatussimilar to that disclosed in a patent application of C. H. Fetter et al.Serial No. 673,882, filed June 1, 1933 which issued as Patent 2,037,161on April 14, 1936. Both of these patents and the above application arehereby made part of this application.

Line |63 is also shown connected to bus-bars 56 4and extends to a powerhouse |0| which includes Fig. 4, as well as part of Fig. 3. Line |63extends to a switchboard ||0 at the power house. This switchboard isassumed to be a central switchboard for the entire power system fromwhich various switching arrangements and load divisions in the powersystem are controlled. Located in this switchboard are clocks |03 and|04. Clock |03 is connected to line |63 and indicates the correct timewhile clock |04 is connected to the power system and indicates the timeindicated by electric clocks connected to the power system.

A group of variable phase shifting or adjusting devices |05, |06, |01,|08, and |09 are located in or near control board ||0 and are controlledfrom this board. These phase Shifters or adjusters are connected to line|63 and may be any suitable form as, for example, somewhat similar tothe phase shifting device shown in Fig. 2. One of these phase shiftingdevices is provided for each generator or power house, the load of whichit is desired to control from the central point. From these phaseshifting devices lines extend to the various power houses and generatorsof the system to be controlled from this central power house or controlboard. For example, line 2 |3 from phase shifter |05 extends to anoutlying power system ||6 through amplifier ||5. This outlying powersystem ||6 may, at times, be connected to the power system controlledfrom board ||0 or may be entirely independent of the power system towhich power house |0| is connected. Lines ||8 and ||9 from the variablephase shifters |06 and |01 extend to the control apparatus associatedwith generators in the power house |0| and illustrated within the brokenlines |51 and |56 (Fig. 4). This control apparatus may be of anysuitable form such as apparatus for comparing the times indicated by twoclocks similar to |03 and |04, one of which is run from the power systemand the other from the standard frequency system and then controllingthe frequency of the power system in accordance with the difference inthe two clocks. Two forms of apparatus for doing this are shown in U. S.Patents 1,310,372 granted on July 15, 1919 to A. F, Poole and 1,505,925granted on August 19, 1924 to H. E. Warren. However, the preferredmanner of regulating the frequency of the power system from the standardfrequency current is shown in Fig. 4.

Referring now to Fig. 4, line ||8 from phase shifter |06 is connected toan improved modulator similar to the one disclosed in U. S. patent to W.A. Marrison, 1,762,725, June 10, 1930. The modulator shown in Fig. 4does not require any phase splitting device as shown in the patent. Line||8 from the phase adjusting arrangement |06 is connected to the primarysides of three transformers |20, |2| and |22. The secondaries of thesetransformers are balanced and connected to tubes |23 and |24, |25 and|26, and |21 and |28, respectively. These tubes may be the usual highvacuum tubes or they may be of the gas or thyratron type dependinglargely on amount of torque required -for the polyphase control motor,since both types function equally well. The gas or thyratron type,however, is usually employed where more output power is required. Theplate power for these tubes is supplied from a three-phase power supplysystem through transformer bank |31. 'Ihis power is supplied from thepower system or by alternator |36, the frequency and phase of which itisdesired to control. 'I'his plate supply power for these tubes isconnected to the output circuit of the tubes through windings |29, |30and |3| of motor |32. If the phase of both generator |36 and thestandard frequency .from the variable phase shifter |06 over line ||8remains constant, motor |32 will remain stationary. However, should thephase of either system vary, motor |32 will rotate in accordance withthe variations. Motor |32 is connected to the governor |34 and maychange the governor limits or in any other way control the prime mover|35 driving generator |36. Governor |34 may be provided with the usualconnections, illustrated by lines |6|, to the power system forcompensating for load variations and other usual disturbances so thatless control will be required by motor |32 and thus insure a moreconstant frequency. A feature of this modulating and controllingarrangement is that in case some trouble occurs to the line or apparatussupplying the standard frequency current so that this current isinterrupted, motor |32 will remain in substantially its position at thetime of the trouble and thus maintain the power frequency or thegovernor limits at the best known values.

Line I9 from variable phase shifter |01 is connected in a similar mannerto the generator and associated apparatus illustrated within broken line|56. As pointed out above, should the frequency of this generator varyappreciably from that of the standard frequency, the control motor isactuated so as to correct the frequency of this generator. By adjustingthe relative phases of the standard frequency current supplied to thesetwo generators shown within broken lines |56 and |51, the relative loadsupplied by each generator may be readily controlled since motor 214associated with generator and control apparatus |56, for example, isactuated bythe relative phase and frequency of the standard frequencysupplied over line ||9 and that of the power system frcquency. The sameapplies to generator shown within the broken line |51 so that if thestandard frequency current supplied to these two control circuits variesin phase, the associated motor will cause a corresponding change in thegovernors controlling the two generators so that the generators willsupply the desired amounts of power. These generators are connectedthrough a transformer bank |40 to a power transmission line |4|.

The output from variable phase shifting or adjusting devices |08 and |09pass through carrier equipment and |i3 and through the power linecarrier coupling equipment |2 and I 4 which are, in turn, connected topower line |4|. This carrier equipment and ||3 changes the frequency ofthe standard frequency current so that it will pass over differentchannels of the carrier equipment.

Fig. 5 shows power switching stations |42 and |46 to which are connectedload centers, such as |44, by means of lines |43 and 215. These loadcenters contain clock systems, such as |46, which are preferably run bysynchronous motors from the power system. However, it should beunderstood that in case it is so desired, a clock syst-em may be runfrom the carrier current supplied over the power system. A generatingand switching station is also shown at |45 connected to another load.This generator equipment may be similar to that shown in Fig. 4 or 6 ormay be controlled in any other suitable manner.

Referring now to Fig. 6, the operation of an outlying connected powerstation will be described, as well as the manner in which it iscontrolled from the central station of switchboard ||0. Here, carrierequipment |48 is coupled through power line coupling equipment |41 tothe power system |4|. Assume that the carrier equipment |48 selects thecarrier current channel controlled by carrier current equipment of Fig.3 and converts the carrier current received from this channel into asuitable low frequency current, the phase of which is controlled from|08. A secondary frequency standard source |49 may be connected andcontrolled by this standard frequency received over the line. U. S.patents to H. Nyquist, 1,684,455, September 18, 1928; H. A. Affel,1,740,491, December 24, 1929; and W. A. Marrison, 1,931,873, October 24,1933, show suitable methods of controlling the frequency of thesecondary source of standard frequency current and are hereby made partof this description. This secondary source is provided to control thegenerators at this power house in case some trouble occurs in thecarrier equipment or in the power line supplying the carrier current tothis station which prevents the reception of the control current. It isto be understood, however, that this secondary source may be omittedwherever it is not required without affecting the operation of thesystem. If the central control board ||0 of the power system is somedistance from the source of standard frequency, it may be desirable toprovide a secondary standard frequency source similar to |49 at thiscentral control board. Such a source might also be employed at eachmajor or frequency control station of the power system.

The standard frequency current also supplies current for operating clock|50 (see Fig. 6) which is located adjacent clock |5I. Clock |5| issupplied from transformer |52 and the power bus |53 of the station;Variable phase shifting or adjusting devices |58 and |59 are providedfor each of the generators shown within the broken lines |54 and |55 sothat the loads may be divided between these generators in any suitablemanner. The output from these generators is connected to the powertransmission line through transformer bank |60. These generators arecontrolled in a manner similar to that described for those shown in Fig.4 so that any change in the phase of the constant frequency current willcause a correspending change in the load supplied to the power system bythese generators. In case it is desired to control the load supplied tothe system by the outlying power house shown in Fig. 6 from the centralswitchboard H0, all that is necessary is that the phase of the constantfrequency current transmitted to the carrier system be adjusted by thevariable phase adjuster |08. Thus, it is possible to control the load oneach of the power generators of a system as well as the exchange ofpower between various power generating sta-' been shown or described butit is understood that it will be provided when necessary.

Fig. '7 shows an alternative arrangement for shifting the phase of thestandard frequency current which is suitable for standard frequencycurrents of higher frequency than that shown in Fig. 2. The arrangementshown in Fig. 2 is suitable for shifting the phase of currents up to say100 kilocycles per second while that shown in Fig. 7 is more suitablefor shifting the phase of a standard frequency current having afrequency above 100 kilocycles. Here, coil |64 is connected to thesource of standard frequency current supplied to terminals Coil |64 isinductively coupled to coils |65 and |66. Coil |65 is tuned by means ofcondenser |61 so that the combination resonates at a frequency slightlybelow the standard frequency current, while coil |66 is tuned by meansof condenser |68 so that this combinationresonates atafrequency slightlyabove the standard frequency current so that the voltages acrosscoils|65and |66 are substantially ninety degrees out of phase with eachother. These voltages are appliedto the grid or input circuits of tubes|69 and |10. Tubes |69and |10 are provided, as in Fig. 2, to reduce theeffects of stray fields upon these quadrature currents. The outputs ofthese tubes |69 and |10 are connected to coils |13, |15 and |14, |16,respectively. Condensers |1| and |12 are also connected to the outputcircuits of the tubes |69 and |10 and are used to resonate the coils|13, and |14, |16, as well as make minor adjustments in the phase of theoutput currents supplied to these coils so that they will besubstantially in phase quadrature. These coils |13, |15 and |14, |16have their axes at right angles to each other so that they will producea rotating magnetic field which rotates at the speed of the standardfrequency when supplied by the current from tubes |69 and |10.

Coil |11 is mounted on shaft 16 and connected to slip rings 45 and 46which in turn are connected to the input circuit of tube 41. In thiscase a resistance |18 is provided in series with the input circuit inorder to further reduce the effect of the impedance of the input circuitof the tube 41 upon the phase of the current induced in coil |11. Coil|11 is mounted on shaft 16 so that it rotates in the center of the fieldproduced by coils |13, |15 and |14, |16. If this coil |11 is rotated AFrevolutions per second as before it will then haveinducedinitavoltagehaving a frequency of FAF where F is the frequency of the standardfrequency current.

The phase regulating device shown in Fig. 8 is similar to that describedin a patent application of L. A. Meacham Serial No. 686,352 filed August23, 1933 and issued as Patent No. 2,004,613 on June 11, 1935 andoperates in a slightly different manner than that described for Fig. 2.Here the standard frequency is supplied to terminals 5| as before. Theprimary windings of transformers |8|'and |82 are connected in serieswith each other' and to terminals 5|. Eachl of the primary windings hasconnected in parallel with it a phase adjusting network such as |19 andIl. The secondary winding of transformer |8| is connected to thestationary condenser plates |83 and |84, while the secondary oftransformer |02 is connected to the stationary condenser plates |86 and|81. These condensers are similar to those used 'in tuning radioreceivers. However, the rotary plates are shaped as described in apatent application of L. A. Meacham, Serial No. 686,352, filed August23, 1933 which issued as Patent 2,004,613 on June 11, 1935. Only one setof rotary plates |85 is provided for the stationary plates |63 and |84and a second set of similar rotary plates |88 is provided for thestationary plates |86 and |81. These sets of rotor plates are mounted onshaft |90 at right angles to each other and ar-e connected together andto transformer |89. Transformer |89 has its secondary connected toterminals 50 and to the input circuit of vacuum tube 41 the output ofwhich is connected through the output transformer 48 to terminals 49. Asin Figs. 2 and 7, tube 41 is provided to prevent the output or loadimpedance from affecting the output frequency. Condensers 2.15, 2|6,2|`| and 2|8 are connected in parallel with stationary plates |83, |84,|86 and |81 and are used to adjust for any irregularities anddifferences in the capacities of these plates. It may not be necessaryto provide all of these condensers, instead only one or two may benecessary in parallel with those plates which have the least amount ofcapacity.

Shaft |96 is rotated through gears |9| and |62 which in turn are rotatedby wheel |93. Wheel |93 is rotated by means of disc |94 which rests ontop of it. As disc |94 rotates, it rotates wheel |93 due to the frictionbetween this wheel and the disc. Wheel |94 is rotated by pin |95 whichis attached to shaft |91. Disc |94 is arranged so that it is free toslide up and down along shaft |91 so that it will alwaysv press againstwheel |93 with a force sufficient to provide friction between it andwheel |93 to rotate wheel |93. Shaft |91 is rotated through gears |98and |99 and shaft 200 by motor 20|. Motor is mounted on springs 202which in turn aremounted on a carriage 201. Carriage 201 is supported bymeans of screw 204 which is mounted in members' 265 and 206. Screw 204is rotated by knob 210 through gears 209 and 208. Attached to gear 209are gears 2|| and 2|2 which rotate counters 2|3 and 2| 4. These countersare used to indicate the position of motor 20|. By rotating knob 2| 0and screw 204, motor 20| is caused to move back and forth along screw204.

This causes disc |94. also to move past wheel |93 and thus change therelative rates of rotation of disc |94 and wheel |93. Screw 204 is longenough to move disc |94 so that wheel |93 can make contact with disc |94at either edge oranywhere in between so that not only may the relativerates of rotation of wheel |93 and disc |94 be varied, but also therelative directions of rotation. Thus, as shown, with wheel |93 to theright of shaft |91, it will rotate in one direction whereas if it is tothe left of shaft |91 it will rotate in the opposite direction withshaft |91 rotating in the same direction. Motor 20| is provided with acentrifugal contact 2|9 which is connected to alarm circuit 220. Thesecontacts are provided to give an alarm. in case motor 20| stops for anyreason. Motor 20| is preferably a synchronous motor which may besupplied with power either from a regulated power system or from thestandard frequency current supply system.

The operation of this system is somewhat different from that describedfor Fig. 2. Assume that the phase regulating arrangement shown in Fig. 8is connected in place of the one shown in Fig. 2 and that the clock 55is 0.05 of a second fast when compared with time signals or otherobservations. In this case knob 2|!) will ba turned so that registers2|3 and 2| 4 will indicate that during the next twenty-four hours, motor20| will turn shaft |90 through gears |9|, |92, and wheel |93 and disc|94 so as to correct for this error. It may be set so as to maintain thefrequency as nearly correct as possible in which case at the end of atwenty-four hour period or any other suitable period the clock willstill read 0.05 of a second slow or it may be set so that at the end ofthis period clock 55 will read the exact time. The manner in which therotation of the movable condenser plates |85 and |88 with shaft |90advances or retards the phase of the standard frequency is described indetail in a patent application of L. A. Meacham, Serial No. 686,352, ledAugust 23, 1933, and issued as Patent 2,004,613 on June 11, 1935, whichapplication and patent is hereby made part of this specification.

It should be noted that with the regulating device shown in Fig. 2 theintegrated phase of the standard frequency current or the time indicatedby the clocks operated by this current is periodically adjusted orregulated at a uniform rate while with the device shown in Fig. 8 thephase of the standard frequency current is continuously and uniformlyadjusted or regulated in accordance with the best available past andpresent observations of some periodically recurring natural phenomenonsuchas time signals. This continuous and uniform adjusting of the phaseof the standard frequency current amounts to a small change in thefrequency since the phase of an alternating current cannot be changedwithout changing the frequency and the frequency cannot be changedwithout changing the phase. However, since the correction or change madeto fthe standard frequency is very small it has been called a phasechange in this specification and appended claims. In the case of thepower frequency both the terms frequency and phase are employed sincethe usual variations of frequency are much greater.

In some cases such as those in which the frequency of the standardcurrent is of major importance, it may be necessary or desirable toemploy a system operated as described for Fig. 8 while in other cases,such as those in which the integrated phase or time indicated by clocksoperated by the standard frequency is of major importance a system suchas described in Fig. 2 is preferable. Sometimes it may be desirable toemploy both methods, that is, pass the standard frequency currentsthrough a frequency adjusting mechanism in accordance with Fig. 8 andthen through a time adjusting mechanism in accordance with Fig. 2. Incase it is desired to have the standard frequency current adjusted inaccordance with each method, it may be desirable to employ anarrangement in accordance with Fig. 8 in the standard frequency or timesystem illustrated in diagrammatic form at 26 in Fig. 2 and at the sametime employ the phase regulating system shown in Fig. 2 for the otherparts of the system. In this case the system shown at 26 may be used toregulate watches, clocks, radio stations and the like while the systemshown in Figs. 2 to 6 may be used to provide a standard time service. Inaddition, it is to be noted that systems or apparatus shown in Figs. 2,7 and 8 may be operated in either manner. That is, to continuouslyregulate the phase or to intermittently regulate the phase of thestandard frequency current.

Fig. 9 shows a modulator employing relays instead of tubes which may beused in place of the modulator shown in Fig. 4 for comparing thestandard frequency with the power frequency. Here relays 220, 22| and222 are connected through line 2|9 to the source of phase adjustedstandard frequency current. These relays 220, 22| and 222 are preferablypolar relays and follow the standard frequency. That is, they close onecontact during one-half of the cycle and other contact during the otherhalf of the cycle. The contacts of these relays are connected to thethree-phase power from the generator through transformer bank 230', eachphase of the power current being connected to the contacts of one of therelays through copper-oxide rectifiers and to one of the windings ofmotor 231 so as to produce a rotating eld and rotate armature 231 of themotor in case there is any phase or frequency variation between thestandard frequency and the power frequency. The rotation of this motorin turn rotates shaft 238 which is connected to governor 239. Governor239 may be also controlled by the load on generator 25| by leads 240.Governor 239 controls the prime mover 250 which drives the generator 25|which supplies power to the power system through switch 281.

Fig. 10 shows a modulator suitable for use in comparing a standardfrequency with a single phase power system and controlling a singlephase generator in accordance with the phase and frequency differencesof the two systems. The primaries of transformers 253 and 255 areconnected to a standard frequency source over line 252. The secondarywindings of these transformers are tuned by means of condensers 254 and25S so that the voltages across the secondaries Will be ninety degreesout of phase with each other. The voltages are then applied to tubes259, 260, 26| and 262. The output circuits of these tubes are connectedto windings 263 and 264 of motor 265 in such a manner as to produce arotating magnetic eld in accordance with the difference between thepower frequency and the standard frequency. It should be noted that boththe lament and plate voltages for these tubes are supplied by means oftransformers 251 and 258 which are connected to the power system throughtransformers 212. Motor 265 in turn romotor 265 they may be of thegas-filled, discharge,

or thyratron type of tube. Either type of tube functions equally well inthis circuit and since the losses of the gas-filled type are less, theyprobably would be preferred. V 'A In some cases the power available tooperate the motor from the modulator may be insufficient in which caseit will be necessary to amplify the torque of these motors.` Fig. 11shows one method of doing this. Here motor |32 rotates shaft |33 whichis coupled to an insulated coupling 213 which in turn rotates thecontact arm 216. Contact is made from arm 216 by means of slip ring andbrush 214. The shaft 286 from the governor or throttle of the primemover carries a gear 280 and slip rings 284 and 285. Mounted on thisgear 280 are two contacts 215 and 211 which are connected through theslip rings to motor 283 so that when motor |32 rotates contact arm 216so that` it makes contact with contact member 215, motor 283 will rotateshaft 282 and gear 28| in such a direction as to rotate gear 280 andcontact 215 mounted thereon away from contact 216. The power of motor283.may be as large as necessary andthe speed may be reduced throughgears 28| and 28|] sovthat the torque available to turn shaft 286 isincreased.

The object of the above description of a specific standard frequencysystem in which the phase of the standard frequency is regulated andseveral specific ways illustrate the manner of employing this standardfrequency for certain specific uses is to illustrate this invention, butis not to limit or restrict its scope as defined in the following;claims.

What is claimed is:

l. A standard frequency alternating current system comprising a sourceof standard frequency alternating current, and means operatingindependently of said source connected to said standard frequencycurrent source for continuously and uniformly shifting the phase of saidstandard frequency current source.

2. A standard frequency alternating current system comprising a sourceof standard frequency alternating current, and means operatingindependently of said source connected to said source for intermittentlyregulating the phase of said standard frequency alternating current at auniform rate.

3. A standard frequency system comprising a primary standard frequencysource, a distributing network connected to said source, secondarystandard frequency sources connected to said network, means forcontrolling said secondary standard frequency sources from said primarystandard frequency source, and devices actuated by standard frequencycurrent connected to said secondary standard frequency sources.

4. In a constant frequency system, means for shifting the phase of aconstant frequency current any given phase angle at a uniform rate whichcomprises an input and an output circuit, means connected to said inputcircuit for secur- 5. Means for continuously shifting the phase of analternating current comprising an input and an output circuit, acondenser and a resistance connected in series and to said input circuitfor securing voltages in phase quadrature, two space discharge `deviceshaving their. input circuits connected to said resistance and condenser,a compressed permalloy dust ring having two sets of windings woundthereon which produce two magnetic fields across s aid ring which are atright angles to each other, said windings being connected to said spacedischarge devices for producing a rotating magnetic field when energizedfrom said space discharge devices, a pickup coil wound on a compressedpermalloydust core located in said magnetic field, means forcontinuously rotating said pick-up coil for continuously shifting thephase of the current induced therein, a third space discharge devicehaving its input connected to said pick-up coil and its output connectedto said output circuit for substantially eliminating the effects ofchanges in the output circuit upon the frequency and phase of thecurrent induced in the pick-up coil.

6. A constant frequency system comprising a source of constant frequencycurrent, a phase regulator connected to said source, and time indicatingdevices connected to said phase regulator.

7. A distributing system comprising a plurality of synchronouselectrical clocks, an electrical current distributing network to whichsaid clocks are connected, phase regulating means connected in saidnetwork for compensating for changes of said networks, a source ofstandard frequency current connected to said network, a source of timesignals, means for comparing the time indicated by said clocks withstandard time signals, and means for adjusting the phase of current fromsaid standard frequency source whereby said clocks can be simultaneouslyadjusted to indicate the correct time.

8. A system which comprises in combination a standard frequency systemhaving a source of alternating current the frequency of which issubstantially constant, a phase regulating device for regulating thephase of the alternating current received from said source and adistributing network connected to said device, and a plurality of clocksystems connected to said network and controlled by said standardfrequency.

9. A system, in accordance with claim 8, in Which certain of saidelectrical clock systems are used to regulate and control the frequencyof a power supply system comprising means for comparing the timeindicated by the clocks of said system with the time indicated byelectrical vclocks operated from said power system, and means forcontrolling said power frequency in accordance with the difference inthe time indicated by said clocks.

10. In combination, a three-phase alternating current distributingsystem, a source of standard frequency current, a modulating deviceconnected between each phase of said distributing system and saidstandard frequency current, and means connected to said modulators forcontrolling the frequency of said distributing system.

11. Means for regulating the frequency of a three-phase alternatingcurrent generator from a standard frequency current which comprises amodulating arrangement for modulating each phase of said three-phasealternating current, each of said modulating arrangements including atleast one space discharge device, and means controlled by saidmodulating arrangements for controlling the frequency of the currentgenerated by said generator.

12. In a three-phase alternating current power system, a three-phasegenerator, a source of standard frequency current, a modulatingarrangement which comprises at least one gas-filled tube and circuitarrangement for modulating each phase of said three-phase alternatingcurrent with said standard frequency current, and means for controllingthe frequency of said generator from said modulating arrangements.

13. A polyphase alternating current network comprising a plurality ofgeographically separated alternating current generators connected tosaid network for supplying electrical power thereto, a plurality ofelectrical energy consuming devices connected to said network, a sourceof standard frequency current, means for transmitting said standardfrequency current to said geographically separated generators, and meansfor controlling the frequency and phase of the current generated by saidgenerators in accordance with said standard frequency current.

14. A polyphase alternating current supply network in accordance withclaim 11, comprising means for transmitting said standard frequencycurrent to said geographically separated generators with differentrelative phases whereby the division of load between said geographicallyseparated alternating current generators may be controlled from saidcentral point.

15. An alternating current supply network in accordance with claim l1,in which a means for transmitting said standard frequency current to thegeographically separated alternating current generators comprisescarrier transmitting equipment operating over the supply network of saidsystem.

16. A system for controlling the frequency and phase of a power systemwhich comprises a source of constant frequency current, means forregulating the phase of said constant frequency current, and means forcontrolling the frequency and phase of said power system from said phaseregulated constant frequency current.

17. In combination an alternating current polyphase distributing networkcomprising a plurality of geographically separated alternating currentgenerators connected to said network for supplying electrical powerthereto, a plurality of electrical energy consuming devices connected tosaid network, a plurality of electric clocks driven by synchronousmotors also connected to said networks for indicating time, a source ofstandard frequency current, means for cornparing said standard frequencycurrent with time signals, a phase regulating device connected to saidsource for regulating the phase of said standard frequency current,means for transmitting said phase regulated standard frequency currentto said geographically separated generators, means located at each ofsaid generators for comparing the current of each phase of saidpolyphase currents generated thereby with said phase regulated standardfrequency current and means for controlling the frequency and regulatingphase of said generators in accordance with said phase comparing means.

18. In combination an alternating current network, a plurality ofalternating current generators connected thereto for generating electricpower, a plurality of alternating current electrical energy consumingdevices connected to said network, a plurality of electrical clocksdriven by synchronous motors also connected to said network, a source ofstandard frequency current, means for comparing the frequency of saidpower system with said standard frequency current, means for controllingthe frequency of said generators from said comparing means, means forchecking the phase of said standard frequency current with observationsof some periodically reciu'ring phenomenon, and means for adjusting thephase of said standard frequency current at a specified rate.

19. A standard frequency alternating current system comprising a sourceof alternating current the frequency of which is substantially constant,a phase regulating device for regulating the phase of the currenttransmitted through it, and means for transmitting said constantfrequency current through said phase regulating device.

20. A distributing system comprising a, source of alternating currentthe frequency of which is substantially constant, a plurality orfelectric clocks run by synchronous motors connected to said source ofconstant frequency current, characterized in this that means areconnected between said source and said plurality of clock motors forregulating the phase of said constant frequency current supplied to saidclock motors.

2l. A device for adjusting the phase of an alternating current at auniform rate comprising an input and an output circuit, means connectedto said input circuit for securing two phase currents therefrom, a Spacedischarge device individual to each phase of said two-phase currentconnected to said means, means connected to said space discharge devicesfor securing a rotating magnetic field from said twophase current, and apick-up coil connected in said output circuit, and means for rotatingsaid pick-up coil at a uniform rate in said magnetic field whereby thephase of the output current is varied at a uniform rate in accordancewith the rotation of said pick-up coil.

22. A device for continuously adjusting the phase of an alternatingcurrent comprising an input circuit, an output circuit, means connectedin said input circuit for securing polyphase current therefrom, a spacedischarge device connected to said means individual to each phase ofsaid polyphase current, a ring of magnetic material, a winding woundthereupon for each phase of said polyphase current, and means forconnecting said space discharge devices to said windings for producing arotating magnetic field across said ring by said polyphase current fromsaid space discharge devices, a pick-up coil Wound upon an armature ofmagnetic material, an additional space discharge device connecting saidpick-up coil to said output circuit, and means for uniformly rotatingsaid armature in said rotating magnetic eld whereby the phase of theoutput current is uniformly adjusted.

23. An alternati-ng current distribution network comprising a pluralityof generating sta-I tions, means for controlling the frequency of saidalternating current network which comprises a source of alternatingcurrent the frequency of which is substantially constant, a source oftime signals, means for comparing said source of constant frequencyalternating current with said time signal, means for adjusting the phaseof said constant frequency alternating current at a uniform andspecified rate, means for distributing said phase adjusted constantfrequency current to said generating stations, means for comparing thephase adjusted constant frequency current and the alternating currentgenerated at each of said generating stations, and means for controllingthe current generated by said stations in accordance with the relativephases of said current generated by said stations and said phaseadjusted current.

24. Means for controlling the frequency of the current in an alternatingcurrent distributing network which comprises a source of constantfrequency alternating current, said source having an oscillatorcontrolled by a mechanical vibrating element, a source of time signals,means for com'- paring said constant frequency current with timesignals, means for adjusting the phase of said constant frequencycurrent at a uniform rate, a plurality of alternating current generatorsconnected to said distributing network, a plurality of governorcontrolled prime movers driving said alternators, means for distributingsaid phase Vcorrected constant frequency current adjacent to saidalternators, means for comparing, the frequency and phase of said phaseadjusted constant frequency current with the frequency and phase of thecurrent generated by said alternators, and means for controlling thegovernors of said prime movers which drive said alternators inaccordance with the relative phases of said phase adjusted constantfrequency current and said alternating current generated by saidalternators.

WARREN A. MARRISON.

